Regenerated expandable styrene-based resin particles, regenerated prefoamed styrene-based resin particles, and regenerated styrene-based resin foam molding

Abstract

To provide regenerated expandable styrene-based resin particles which are obtained using a recycled raw material, have stable quality, and exhibit excellent moldability; also provide regenerated prefoamed styrene-based resin particles obtained from such regenerated expandable styrene-based resin particles; and further provide a regenerated styrene-based resin foam molding formed from such regenerated prefoamed styrene-based resin particles.SOLUTION: Regenerated expandable styrene-based resin particles according to an embodiment of the present invention contain 0.001 mass% or more of propane.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to recycled expandable styrene resin particles, recycled pre-expanded styrene resin particles, and recycled styrene resin foamed molded articles.

Background Art

[0002] Foamed molded articles are lightweight, excellent in heat insulation and mechanical strength, and are therefore widely used as heat insulating materials for housing and automobiles, heat insulating materials for building materials, embankment materials for styrofoam civil engineering methods, transportation packaging materials such as fish boxes and food containers, and cushioning materials. Among them, in-mold foamed molded articles manufactured from expandable particles (typically expandable styrene resin particles or pre-expanded styrene resin particles obtained by pre-expanding them) are widely used because they have advantages such as being easy to obtain a desired shape. Such a foamed molded article is composed of a plurality of expandable particles fused to each other.

[0003] On the other hand, the amount of plastic waste is increasing year by year. Most of the plastic waste is disposed of by incineration or landfilling, which has become a major social problem such as environmental pollution, global warming, and a shortage of landfill sites. For this reason, the recycling of plastic waste is strongly demanded socially, and various studies have been conducted on the recycling of plastic waste, such as in response to the implementation of the Home Appliance Recycling Law. Among the various proposed recycling methods, material recycling that reuses plastic waste as a plastic member of a product has attracted attention from the viewpoints of resource circulation and reduction of environmental load.

[0004] Regarding styrene resin foam moldings, material recycling as described above is also being considered. For example, the following reports have been made. Several recycled expandable styrene resin particles using recycled raw materials have been reported. A method for obtaining recycled expandable styrene resin particles by impregnating or press-fitting a foaming agent into recycled resin pellets formed from recovered styrene resin foam moldings has been reported (Patent Document 1). A method for obtaining recycled expandable styrene resin particles by adding styrene monomer to recycled resin pellets formed from recovered styrene resin foam moldings, subjecting them to nuclear polymerization, and then impregnating or press-fitting a foaming agent has been reported (Patent Documents 2 to 4). Recently, recycled expandable styrene resin particles with improved moldability by containing a predetermined amount of normal butyric acid (Patent Document 5) and recycled expandable styrene resin particles with suppressed odor characteristic of recycled materials have been reported (Patent Document 6).

[0005] However, conventionally, recycled expandable styrene resin particles using recycled raw materials have variations in quality, and there are cases where recycled expandable styrene resin particles with stable quality cannot be provided. For example, recycled expandable styrene resin particles using used polystyrene foam as a recycled raw material have a problem that the quality tends not to be stable. Furthermore, such recycled expandable styrene resin particles with unstable quality have a problem that the moldability deteriorates. Note that this state of unstable quality typically means that there are variations in the quality of the resulting recycled expandable styrene resin particles. For example, when the resulting recycled expandable styrene resin particles are foamed, there are differences in the foaming state depending on the product lot, and as a result, the quality of the obtained recycled pre-expanded styrene resin particles and recycled styrene resin foam moldings is also unstable.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

[0007] The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide recycled expandable polystyrene resin particles using recycled raw materials, which have stable quality and excellent moldability. Another object is to provide recycled pre-expanded polystyrene resin particles obtained from such recycled expandable polystyrene resin particles. Furthermore, an object is to provide a recycled polystyrene resin foam molded body molded from such recycled pre-expanded polystyrene resin particles. [Means for Solving the Problems]

[0008] The present inventor has studied the cause of the unstable quality of recycled expandable polystyrene resin particles using conventional recycled raw materials.

[0009]

[0010] ​​​​Therefore, further investigations were conducted on the relationship between the above-mentioned differences in the quality of the recycled raw materials and the above-mentioned foreign matter contamination, and the quality of the recycled expandable polystyrene resin particles. When the blowing agent injected and impregnated during the production of the recycled expandable polystyrene resin particles should be uniformly diffused in the resin particles, due to the above-mentioned differences in the quality of the recycled raw materials and the above-mentioned foreign matter contamination, the uniform diffusion of the blowing agent is inhibited, resulting in uneven quality and unstable quality of the recycled expandable polystyrene resin particles. As a result, the recycled pre-expanded polystyrene resin particles and the recycled polystyrene resin foam molded articles produced from the obtained recycled expandable polystyrene resin particles also have quality variations and cannot maintain stable quality.

[0011] Therefore, the present inventor has intensively studied technical means for promoting the diffusion of the blowing agent in the resin particles using recycled raw materials, and has focused on the use of propane, which has not been actively used as a blowing agent conventionally due to reasons such as safety and handleability. Propane has a higher vapor pressure, higher volatility, and flammability compared to butane and pentane, which are generally used as blowing agents conventionally. By utilizing this high vapor pressure and high volatility, it has been found that the quality of the recycled expandable polystyrene resin particles using the obtained recycled raw materials is stable and excellent in moldability, and thus the present invention has been completed.

[0012] [1] The recycled expandable polystyrene resin particles according to an embodiment of the present invention have a propane content of 0.001% by mass or more. [2] The recycled expandable polystyrene resin particles described in the above [1] may be obtained by injecting a blowing agent into the recycled polystyrene resin particles (A). [3] The recycled expandable polystyrene resin particles described in the above [2] may contain propane as the blowing agent to be injected, and the injection amount of the propane may be 0.01% by mass or more based on the recycled polystyrene resin particles (A). [4] The recycled expandable polystyrene resin particles described in the above [2] or [3] may be such that the recycled polystyrene resin particles (A) are obtained by subjecting styrene-based monomer to core polymerization using recycled polystyrene resin raw material particles (a) as a core. [5] The expandable recycled styrenic resin particles described in the above [2] or [3] may be such that the recycled styrenic resin particles (A) are recycled styrenic resin raw material particles (a). [6] The recycled pre-expanded styrenic resin particles according to the embodiment of the present invention are recycled pre-expanded styrenic resin particles obtained by pre-expanding the expandable recycled styrenic resin particles described in any one of [1] to [5] above, and the bulk expansion ratio of the pre-expansion is 2 to 150 times. [7] The recycled styrenic resin foam molded article according to the embodiment of the present invention is molded from the recycled pre-expanded styrenic resin particles described in the above [6].

Advantages of the Invention

[0013] According to the present invention, it is possible to provide expandable recycled styrenic resin particles using recycled raw materials, which have stable quality and excellent moldability. Further, it is possible to provide recycled pre-expanded styrenic resin particles obtained from such expandable recycled styrenic resin particles. Furthermore, it is possible to provide a recycled styrenic resin foam molded article molded from such recycled pre-expanded styrenic resin particles.

Brief Description of the Drawings

[0014]

Figure 1

Modes for Carrying Out the Invention

[0015] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

[0016] In this specification, when it is described as “(meth)acryl”, it means acrylic and / or methacrylic, and when it is described as “(meth)acrylate”, it means acrylate and / or methacrylate.

[0017] <<A. Recycled Expansible Polystyrene Resin Particles>> The recycled expansible polystyrene resin particles according to an embodiment of the present invention have a particle shape as a whole. The average particle diameter of the recycled expansible polystyrene resin particles is preferably from 0.40 mm to 2.0 mm, more preferably from 0.6 mm to 1.8 mm. The average particle diameter can be measured in accordance with JIS Z 8815. Specifically, the average particle diameter is a value measured as the particle diameter at the 50% integrated value from the particle size distribution by the sieving test of JIS Z 8815.

[0018] As the shape of the recycled expansible polystyrene resin particles according to an embodiment of the present invention, any appropriate shape can be adopted as long as the effects of the present invention are not impaired. Specific examples of such shapes include, for example, spherical, substantially spherical, elliptical spherical (oval), and the like. As the shape of the recycled expansible polystyrene resin particles according to an embodiment of the present invention, in terms of expressing the effects of the present invention, it is preferably spherical or substantially spherical, and more preferably spherical. However, in reality, it is difficult to distinguish between spherical and substantially spherical, so in this specification, both are collectively referred to as spherical.

[0019] The weight average molecular weight of the recycled expansible polystyrene resin particles according to an embodiment of the present invention can adopt any appropriate weight average molecular weight as long as the effects of the present invention are not impaired. Such a weight average molecular weight is preferably from 100,000 to 510,000, more preferably from 110,000 to 490,000, still more preferably from 120,000 to 470,000, and particularly preferably from 130,000 to 450,000.

[0020] The recycled expandable polystyrene resin particles according to the embodiments of the present invention have a propane content of 0.001% by mass or more. That is, the recycled expandable polystyrene resin particles according to the embodiments of the present invention contain 0.001% by mass or more of propane in the resin particles. The recycled expandable polystyrene resin particles according to the embodiments of the present invention can exhibit the effects of the present invention by having a propane content of 0.001% by mass or more. The recycled expandable polystyrene resin particles according to the embodiments of the present invention preferably have a propane content of 0.005% by mass to 5.0% by mass, more preferably 0.008% by mass to 4.5% by mass, still more preferably 0.010% by mass to 4.0% by mass, still more preferably 0.012% by mass to 3.5% by mass, particularly preferably 0.015% by mass to 3.0% by mass, and most preferably 0.020% by mass to 2.5% by mass.

[0021] The propane contained in the recycled expandable polystyrene resin particles according to the embodiments of the present invention can typically be the propane used as a foaming agent to be injected, and can be the propane contained (remaining) in the finally obtained recycled expandable polystyrene resin particles. Since propane has a high vapor pressure, high volatility, and flammability, it has not been actively used as a foaming agent conventionally due to reasons such as safety and handling properties, such as the internal pressure of the reaction vessel during production becoming high pressure. In the recycled expandable polystyrene resin particles according to the embodiments of the present invention, by appropriately using such high vapor pressure and high volatility of propane as a gas for developing expandability, and containing a predetermined amount in the resin particles, an effect of stable quality and excellent moldability can be exhibited. If the propane content in the recycled expandable polystyrene resin particles is too low, the effects of the present invention may not be exhibited. For example, the aging in the production of the recycled expandable polystyrene resin particles may take a long time, resulting in possible variations in quality. If the propane content in the recycled expandable polystyrene resin particles is too high, the effects of the present invention may not be exhibited. For example, due to the high vapor pressure, a large amount of propane may diverge outside the recycled expandable polystyrene resin particles, resulting in possible variations in quality, such as the occurrence of appearance defects in the molded product.

[0022] The recycled expandable polystyrene resin particles according to an embodiment of the present invention may contain, together with propane, an organic compound or an inorganic gas other than propane whose boiling point is equal to or lower than the softening point of the styrene resin and which is gaseous or liquid at normal pressure, in terms of more effectively expressing the effects of the present invention. Examples of the organic compound include aliphatic hydrocarbons such as butane (n-butane, isobutane), pentane (n-pentane, isopentane, neopentane), and n-hexane; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene; ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol, and isopropyl alcohol; low-boiling ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether; and halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane. Examples of the inorganic gas include carbon dioxide gas, nitrogen, and ammonia. Among the above organic compounds and inorganic gases, in terms of more effectively expressing the effects of the present invention, an organic compound whose boiling point is equal to or lower than the softening point of the styrene resin and which is gaseous or liquid at normal pressure is preferable, more preferably at least one selected from the group consisting of butane and pentane, and particularly preferably pentane. Therefore, the recycled expandable polystyrene resin particles according to an embodiment of the present invention preferably contain propane and at least one selected from the group consisting of butane and pentane, and more preferably contain propane and pentane, in terms of further effectively expressing the effects of the present invention.

[0023] When the recycled expandable polystyrene resin particles according to an embodiment of the present invention contain propane and at least one selected from the group consisting of butane and pentane, the content of at least one selected from the group consisting of butane and pentane in the recycled expandable polystyrene resin particles according to an embodiment of the present invention is preferably 20% by mass or less, more preferably 0.5% by mass to 18% by mass, still more preferably 1% by mass to 17% by mass, particularly preferably 2% by mass to 16% by mass, and most preferably 3% by mass to 15% by mass.

[0024] The recycled expandable polystyrene resin particles according to the embodiment of the present invention are preferably obtained by press-fitting a foaming agent into recycled polystyrene resin particles (A), and typically, the following two embodiments can be mentioned. Embodiment (1): Recycled expandable polystyrene resin particles obtained by press-fitting a foaming agent into recycled polystyrene resin particles (A), wherein the recycled polystyrene resin particles (A) are recycled expandable polystyrene resin particles obtained by subjecting styrene-based monomer to core polymerization using recycled polystyrene resin raw material particles (a) as a core. Embodiment (2): Recycled expandable polystyrene resin particles obtained by press-fitting a foaming agent into recycled polystyrene resin particles (A), wherein the recycled polystyrene resin particles (A) are recycled expandable polystyrene resin particles which are recycled polystyrene resin raw material particles (a).

[0025] The recycled expandable polystyrene resin particles according to the embodiment of the present invention have a high environmental contribution degree. The recycled expandable polystyrene resin particles in the above Embodiment (1) preferably have a recycling rate of 10% or more, more preferably 20% or more, still more preferably 25% or more. The recycled expandable polystyrene resin particles in the above Embodiment (2) preferably have a recycling rate of 50% or more, more preferably 70% or more, still more preferably 90% or more, particularly preferably 95% or more, and most preferably 100%. The recycling rate is the ratio of the recovered styrene-based resin in the styrene-based resin contained in the recycled expandable polystyrene resin particles.

[0026] Hereinafter, first, the above Embodiment (1) and Embodiment (2) will be described.

[0027] ≪A-1. Preferred Embodiment (1) of Recycled Expandable Polystyrene Resin Particles≫ One preferred embodiment (1) of the recycled expandable polystyrene resin particles of the present invention is recycled expandable polystyrene resin particles obtained by press-fitting a foaming agent into recycled polystyrene resin particles (A), wherein the recycled polystyrene resin particles (A) are recycled expandable polystyrene resin particles obtained by subjecting styrene-based monomer to core polymerization using recycled polystyrene resin raw material particles (a) as a core.

[0028] <A-1-1. Recycled Styrene Resin Particles (A) in Embodiment (1)> The recycled styrene resin particles (A) in Embodiment (1) are obtained by subjecting styrene monomers to core polymerization using recycled styrene resin raw material particles (a) as a core.

[0029] The recycled styrene resin raw material particles (a) may be only one kind or two or more kinds.

[0030] As the material of the recycled styrene resin raw material particles (a), any appropriate recycled styrene resin can be adopted as long as the effects of the present invention are not impaired. Examples of such recycled styrene resins include recycled products of plastic materials used in, for example, expanded polystyrene (molded products such as fish boxes and agricultural boxes, cushioning materials, block molded products, etc.), expanded sheets (tray containers, sheet scrap materials, etc.), household electrical appliances, packaging containers, cushioning beads, etc.

[0031] The recycled styrene resin raw material particles (a) may contain other recycled resins other than any appropriate recycled styrene resin as long as the effects of the present invention are not impaired. Examples of such other recycled resins include, for example, AS resin, ABS resin, HIPS (high impact polystyrene); polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate (PC); polyamide resins such as nylon (PA); polyolefin resins such as polyethylene (linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP), EVA (ethylene-vinyl acetate copolymer)). The other resins may be only one kind or two or more kinds. In this specification, the recycled resins of the above AS resin, ABS resin, and HIPS (high impact polystyrene) are not included in the category of the above recycled styrene resins.

[0032] As the recycled styrene resin raw material particles (a), molded articles made from products named "Epstrem" or "Eslen Beads RNW" manufactured by Sekisui Chemical Co., Ltd. may be adopted.

[0033] As the recycled styrene resin raw material particles (a), pulverized products obtained by pulverizing recycled resins obtained by heating and / or reducing the volume of used foamed styrene resins may be adopted. As the recycled styrene resin raw material particles, they may be in the form of pellets obtained by extruding and pelletizing this pulverized product, or they may be those obtained by further pulverizing these pellets. Or, they may be those obtained by volume reduction recovery using a solvent such as limonene.

[0034] The recycled styrene resin raw material particles (a) are preferably pellets obtained by the melt extrusion method. The melt extrusion method is typically a method in which pulverized products, ingots, foamed particles, etc. of used styrene resins are supplied to a resin supply device, melted within the resin supply device, extruded from small holes of a die attached to the tip of the resin supply device, and then cooled to obtain pellets.

[0035] As the pellets obtained by the above melt extrusion method, preferably, at least one selected from extrusion strand pellets obtained by extruding used foamed styrene resin with an extruder and performing strand cutting, underwater cut pellets obtained by the underwater cutting method of extruding used foamed styrene resin with an extruder and cutting it underwater at the same time, and hot cut pellets obtained by the hot cut method of cutting and cooling used foamed styrene resin particles immediately after they come out of the die of the extruder.

[0036] As the recycled styrene resin raw material particles (a), the pellets obtained by the above melt extrusion method may be used as they are, or in order to obtain pellets of a smaller size, they may be made into so-called "mini-pellets" again by the melt extrusion method or the like.

[0037] As the recycled styrene resin raw material particles (a), a shrinkage product or a melt of a foamed styrene resin obtained by coarsely pulverizing a used foamed styrene resin to an appropriate size as necessary and then performing heat shrinkage, shrinkage by bubble destruction due to compression, shrinkage due to frictional heat, melting, etc. may be used.

[0038] Examples of the used foamed styrene resin include a molded product obtained by molding a foaming styrene resin and a product obtained by heating and foaming the molded product.

[0039] The recycled styrene resin raw material particles (a) can contain at least one selected from the group consisting of fine powdery inorganic substances and organic lubricants. Typically, these can function as bubble regulators.

[0040] Examples of the fine powdery inorganic substances include talc, calcium carbonate, silica, mica, and sodium bicarbonate. Here, talc typically refers to a mixture mainly composed of silicon oxide and magnesium oxide and containing trace amounts of aluminum oxide, iron oxide, etc.

[0041] The average particle diameter of the fine powdery inorganic substance is preferably 100 μm or less, more preferably 30 μm or less. If the average particle diameter of the fine powdery inorganic substance exceeds 100 μm, the effect of reducing the bubble size of the recycled pre-expanded styrene resin particles may decrease.

[0042] The content ratio of the fine powdery inorganic substance is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 2% by mass, based on the recycled styrene resin raw material particles (a). If the content ratio of the fine powdery inorganic substance based on the recycled styrene resin raw material particles (a) is less than 0.1% by mass, the effect of reducing the bubble size of the recycled pre-expanded styrene resin particles may decrease. If the content ratio of the fine powdery inorganic substance based on the recycled styrene resin raw material particles (a) exceeds 5% by mass, the bubble size of the recycled pre-expanded styrene resin particles will become extremely small, and the recycled pre-expanded styrene resin particles may melt during molding, resulting in deterioration of the appearance of the molded product.

[0043] Examples of the organic lubricant include paraffin; polyethylene glycol; silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane; higher fatty acid bisamides such as methylene bisstearic acid amide, ethylene bisstearic acid amide, and ethylene bisoleic acid amide; and metal salts of higher fatty acids such as zinc stearate, magnesium stearate, and zinc oleate.

[0044] The content ratio of the organic lubricant is preferably 0.01% by mass to 2.0% by mass, more preferably 0.02% by mass to 1.8% by mass, and in some cases, even more preferably 0.02% by mass to 0.2% by mass, and particularly preferably 0.02% by mass to 0.1% by mass, based on the recycled styrene resin raw material particles (a). If the content ratio of the organic lubricant based on the recycled styrene resin raw material particles (a) is less than 0.01% by mass, the effect of reducing the bubble size of the recycled pre-expanded styrene resin particles may be reduced. If the content ratio of the organic lubricant based on the recycled styrene resin raw material particles (a) exceeds 2.0% by mass, the bubble size of the recycled pre-expanded styrene resin particles becomes extremely small, and the recycled pre-expanded styrene resin particles may melt during molding, resulting in a tendency for the appearance of the molded product to be inferior.

[0045] Specific methods for including at least one selected from the group consisting of fine powder inorganic substances and organic lubricants in the recycled styrene resin raw material particles (a) include, for example, a method of kneading at least one selected from the group consisting of fine powder inorganic substances and organic lubricants during extrusion molding. In this case, preferably, after mixing the pulverized material and the bubble regulator in advance, extrusion molding is performed. The mixing method of the pulverized material and the bubble regulator can be performed by any appropriate method within a range that does not impair the effects of the present invention. Examples of such methods include mixing methods using mixers such as tumblers, ribbon blenders, V blenders, Henschel mixers, and Lodige mixers.

[0046] The recycled styrene-based resin raw material particles (a) are preferably heat-melted for the purpose of specific gravity adjustment. In this step, the specific gravity of the recycled styrene-based resin raw material particles (a) is preferably adjusted to 0.6 or more, more preferably 0.9 or more. If the specific gravity of the recycled styrene-based resin raw material particles (a) is less than 0.6, the dispersion of the recycled styrene-based resin raw material particles (a) is unstable, so there is a risk that oversized particles will be generated during the subsequent polymerization step and the yield will decrease. The heat melting of the recycled styrene-based resin raw material particles (a) can be carried out by any appropriate method as long as the effects of the present invention are not impaired. Examples of such methods include those using an extruder or a hot roll. The heat melting is preferably cooled and solidified in a state where no strain remains in the obtained resin or the strain is small. If strain remains in the resin particles, the strain will be relaxed in the subsequent process, causing contraction in the stretching direction, and the resulting recycled foamed styrene-based resin particles may not be spherical but flat. Therefore, as the heat melting, it is preferable to perform non-stretched melting using an extruder. If the heat melting is carried out in a stretched state, there is a risk that strain will remain in the stretched resin obtained by cooling and solidifying. Even if strain remains in the resin due to heat melting, the strain can also be relaxed by aging at a temperature equal to or higher than the softening point of the resin for a certain period of time.

[0047] When obtaining the recycled styrene-based resin raw material particles (a), any crusher can be employed as long as the effects of the present invention are not impaired. Examples of such crushers include, for example, crushers for plastics, and crushers for polystyrene are preferred.

[0048] The recycled styrene-based resin raw material particles (a) can be sieved as necessary and then melted again using an extruder or the like.

[0049] The average particle diameter of the recycled styrene resin raw material particles (a) is preferably from 0.2 mm to 3.0 mm, more preferably from 0.3 mm to 2.5 mm, still more preferably from 0.4 mm to 2.0 mm, and particularly preferably from 0.5 mm to 1.7 mm. When the average particle diameter of the recycled styrene resin raw material particles (a) exceeds 3 mm, the shape of the obtained recycled expandable styrene resin particles may not easily become spherical. When the average particle diameter of the recycled styrene resin raw material particles (a) is less than 0.2 mm, the obtained recycled expandable styrene resin particles may adhere to each other.

[0050] The L (long side) / D (short side) of the recycled styrene resin raw material particles (a) is preferably from 1.0 to 6.0, more preferably from 1.0 to 5.0, still more preferably from 1.0 to 4.0, particularly preferably from 1.0 to 3.0, and most preferably from 1.0 to 2.5. When the L (long side) / D (short side) of the recycled styrene resin raw material particles (a) is outside the above range, the shape of the obtained recycled expandable styrene resin particles may not easily become spherical.

[0051] It is preferable that the content of particles having an average particle diameter of 200 μm or less in the recycled styrene resin raw material particles (a) is less than 1% by mass. When the content of particles having an average particle diameter of 200 μm or less in the recycled styrene resin raw material particles (a) is 1% by mass or more, the appearance of the recycled expandable styrene resin particles obtained using the same may deteriorate.

[0052] The weight average molecular weight of the recycled styrene resin raw material particles (a) is preferably from 100,000 to 510,000, more preferably from 150,000 to 490,000. If the weight average molecular weight of the recycled styrene resin raw material particles (a) is less than 100,000, sufficient strength may not be obtained. When the weight average molecular weight of the recycled styrene resin raw material particles (a) exceeds 510,000, the recycled styrene resin raw material particles may not easily become spherical, or the expandability may decrease and the appearance of the molded product may be inferior.

[0053] The styrene monomer used for the core polymerization may be only one kind or two or more kinds.

[0054] The styrenic monomer includes styrene or a styrene derivative. Examples of the styrene derivative include α-methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, i-propylstyrene, dimethylstyrene, bromostyrene, and the like. The styrenic monomer may be only one kind or two or more kinds. The styrenic monomer preferably contains at least styrene. The content ratio of styrene to the total amount of the styrenic monomer is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more.

[0055] The styrene monomer may contain a vinyl monomer other than any appropriate styrene monomer as long as the effects of the present invention are not impaired. For example, polyfunctional monomers, (meth)acrylate monomers, maleate monomers, and fumarate monomers can be mentioned. Such vinyl monomers may be only one kind or two or more kinds.

[0056] Specific examples of the polyfunctional monomer include, for example, divinylbenzene such as о-divinylbenzene, m-divinylbenzene, p-divinylbenzene; alkylene glycol di(meth)acrylate such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate; Specific examples of the (meth)acrylate monomer include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hexyl (meth)acrylate. Examples of the maleate monomer include dimethyl maleate. Examples of the fumarate monomer include dimethyl fumarate, diethyl fumarate, and ethyl fumarate.

[0057] In Embodiment (1), from the viewpoint of environmental contribution, the higher the content ratio of the recycled styrenic resin raw material particles (a) to the total amount of the recycled styrenic resin raw material particles (a) and the styrenic monomer, the better. However, from the viewpoint of producing the recycled styrenic resin particles (A) by core polymerization, the content ratio of the recycled styrenic resin raw material particles (a) to the total amount of the recycled styrenic resin raw material particles (a) and the styrenic monomer is preferably 5% by mass to 90% by mass, more preferably 10% by mass to 85% by mass, still more preferably 15% by mass to 80% by mass, still more preferably 20% by mass to 75% by mass, and particularly preferably 25% by mass to 70% by mass.

[0058] In Embodiment (1), the recycled styrenic resin particles (A) are obtained by subjecting a styrenic monomer to core polymerization using the recycled styrenic resin raw material particles (a) as a core. As such a core polymerization method, any appropriate method can be adopted as long as the effects of the present invention are not impaired. As one preferred embodiment of such a core polymerization method, an emulsion containing a polymerization initiator and a styrenic monomer is added to a suspension obtained by dispersing the recycled styrenic resin raw material particles (a) as a core in an aqueous medium to impregnate the recycled styrenic resin raw material particles (a), and then a styrenic monomer is added to conduct polymerization.

[0059] When obtaining the recycled styrene-based resin particles (A), the addition temperature when adding the styrene-based monomer to the recycled styrene-based resin raw material particles (a) is preferably 40°C to 119°C, more preferably 40°C to 118°C, still more preferably 40°C to 117°C, particularly preferably 50°C to 117°C, and most preferably 60°C to 115°C in terms of being able to more effectively exhibit the effects of the present invention. If the addition temperature when adding the styrene-based monomer to the recycled styrene-based resin raw material particles (a) is adjusted within the above range, the styrene-based monomer can be incorporated while maintaining the recycled styrene-based resin raw material particles (a) at an appropriate hardness. Therefore, good spheroidization of the recycled styrene-based resin particles (A) can be achieved, and ultimately good spheroidization and excellent moldability of the obtained recycled expandable styrene-based resin particles can be exhibited. If the addition temperature when adding the styrene-based monomer to the recycled styrene-based resin raw material particles (a) is too low outside the above range, the recycled styrene-based resin raw material particles (a) will become too hard. In this state, when the styrene-based monomer is incorporated, the recycled styrene-based resin particles (A) are less likely to be spheroidized, and there is a possibility that the finally obtained recycled expandable styrene-based resin particles are less likely to be spheroidized and have poor moldability. If the addition temperature when adding the styrene-based monomer to the recycled styrene-based resin raw material particles (a) is too high outside the above range, the recycled styrene-based resin raw material particles (a) will become too soft. In this state, when the styrene-based monomer is incorporated, the recycled styrene-based resin particles (A) are less likely to be spheroidized, and there is a possibility that the finally obtained recycled expandable styrene-based resin particles are less likely to be spheroidized and have poor moldability. Here, the "addition temperature when adding the styrene-based monomer to the recycled styrene-based resin raw material particles (a)" means the addition temperature through the addition of the emulsion containing the polymerization initiator and the styrene-based monomer and the subsequent addition of the styrene-based monomer.

[0060] When obtaining a suspension by dispersing recycled styrene resin raw material particles (a) as nuclei in an aqueous medium, any appropriate method can be adopted as the method for dispersing the recycled styrene resin raw material particles (a) in the aqueous medium, as long as the effects of the present invention are not impaired. Such a dispersion method is preferably a dispersion performed using a device equipped with a stirring blade. As a method for more finely dispersing, a method using a homomixer can be mentioned.

[0061] When obtaining a suspension by dispersing recycled styrene resin raw material particles (a) as nuclei in an aqueous medium, it is preferable to use a dispersant in the dispersion of the recycled styrene resin raw material particles (a) in the aqueous medium. Any appropriate dispersant can be adopted as long as it can be used for suspension polymerization and the effects of the present invention are not impaired. Examples of such dispersants include organic dispersants such as polyvinyl alcohol, polyvinyl pyrrolidone, and methyl cellulose; sparingly soluble inorganic salts such as magnesium pyrophosphate and tricalcium phosphate. Among these, magnesium pyrophosphate is preferable as the dispersant in terms of being able to more effectively exhibit the effects of the present invention.

[0062] The blending ratio of the dispersant with respect to 100 parts by mass of the recycled styrene resin particles (A) is preferably 0.1 part by mass to 2 parts by mass, more preferably 0.1 part by mass to 1.5 parts by mass, and even more preferably 0.1 part by mass to 1.0 part by mass.

[0063] When obtaining a suspension by dispersing recycled styrene-based resin raw material particles (a) as nuclei in an aqueous medium, it is preferable to use a surfactant in the dispersion of the recycled styrene-based resin raw material particles (a) in the aqueous medium. Any suitable surfactant can be employed as long as it can be used in suspension polymerization and does not impair the effects of the present invention. Examples of such surfactants include sodium dodecylbenzenesulfonate, sodium alkanesulfonate, sodium alkylsulfonate, sodium alkyl diphenyl ether disulfonate, and sodium α-olefin sulfonate. Among these, sodium dodecylbenzenesulfonate is preferable as the surfactant in terms of being able to more effectively exhibit the effects of the present invention.

[0064] The blending ratio of the surfactant with respect to 100 parts by mass of the recycled styrene-based resin particles (A) is preferably 0.005 to 0.1 part by mass, more preferably 0.005 to 0.08 part by mass, and even more preferably 0.005 to 0.06 part by mass.

[0065] As the emulsification method for obtaining an emulsion containing a polymerization initiator and a styrene-based monomer, any suitable method can be adopted as long as it does not impair the effects of the present invention. Such a dispersion method is preferably a dispersion carried out using a device equipped with a stirring blade. A method using a homomixer can be mentioned as a method for more finely dispersing. At this time, it is preferable to disperse until the droplet diameter of the dispersion liquid in which the styrene-based monomer is dispersed becomes equal to or smaller than the particle diameter of the nuclei. When added to the aqueous medium in a state where the droplet diameter is larger than the particle diameter of the nuclei, a plurality of recycled styrene-based resin raw material particles (a) are incorporated into the droplets of the dispersion liquid in which the styrene-based monomer is dispersed, resulting in adhesion, plasticization, and coalescence of the recycled styrene-based resin raw material particles (a), and it is easy to generate oversized particles.

[0066] When obtaining an emulsion containing a polymerization initiator and a styrenic monomer, any suitable polymerization initiator can be employed as long as it is used in the suspension polymerization method and does not impair the effects of the present invention. Examples of such polymerization initiators include organic peroxides such as benzoyl peroxide, t-butyl peroxy-2-ethylhexyl carbonate, and t-butyl perbenzoate; and azo compounds such as azobisisobutyronitrile. The polymerization initiator may be only one type or two or more types.

[0067] The usage amount of the polymerization initiator is preferably 0.1% by mass to 1.0% by mass, more preferably 0.1% by mass to 0.8% by mass, and still more preferably 0.1% by mass to 0.5% by mass, based on the styrenic monomer.

[0068] The polymerization initiator is preferably dissolved in the styrenic monomer or a solvent and then added. Examples of the solvent include aromatic hydrocarbons such as ethylbenzene and toluene; and aliphatic hydrocarbons such as heptane and octane. When using a solvent, it is usually used in an amount of 10% by mass or less based on the styrenic monomer.

[0069] As a method of adding the styrenic monomer after adding and impregnating the emulsion containing the styrenic monomer into the suspension containing the recycled styrenic resin raw material particles (a), any appropriate method can be adopted as long as it does not impair the effects of the present invention. Examples of such methods include divided addition and continuous addition. The addition rate is appropriately selected according to the capacity, shape, polymerization temperature, etc. of the polymerization apparatus.

[0070] After adding and impregnating the emulsion containing the styrenic monomer into the suspension containing the recycled styrenic resin raw material particles (a) and then adding the styrenic monomer, if necessary, the polymerization reaction may be continued at any appropriate temperature and time.

[0071] The suspension containing the recycled styrene resin raw material particles (a) or the emulsion containing the styrene monomer may contain a bubble regulator. Examples of such a bubble regulator include fatty acid monoamides such as oleic acid amide, stearic acid amide, and hydroxystearic acid amide; fatty acid bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide.

[0072] <A-1-2. Pressurization of the foaming agent in Embodiment (1)> The recycled foamed styrene resin particles in Embodiment (1) are obtained by pressuring a foaming agent into the recycled styrene resin particles (A). Typically, the foaming agent is pressured in and impregnated into the resin particles.

[0073] Typical methods for pressuring the foaming agent in Embodiment (1) include putting the recycled styrene resin particles (A) into a reactor such as an autoclave and pressuring the foaming agent in.

[0074] The foaming agent may be only one kind or two or more kinds.

[0075] In Embodiment (1), the foaming agent to be pressured preferably contains propane, and the pressured amount of the propane is preferably 0.01% by mass or more, more preferably 0.05% to 10% by mass, still more preferably 0.08% to 7.0% by mass, particularly preferably 0.10% to 5.0% by mass, and most preferably 0.15% to 3.5% by mass, based on the recycled styrene resin particles (A).

[0076] In Embodiment (1), if the pressured amount of propane with respect to the recycled styrene resin particles (A) is too small or too large, the effects of the present invention may not be manifested. For example, there may be variations in quality, leading to a decrease in moldability.

[0077] In Embodiment (1), the blowing agent to be press-fitted preferably contains propane in an amount of 0.1% by mass or more in the entire blowing agent to be press-fitted. That is, propane is contained in an amount of 0.1% by mass or more in the entire blowing agent used for press-fitting. In Embodiment (1), the effect of the present invention can be exhibited by the blowing agent containing propane in an amount of 0.1% by mass or more. In Embodiment (1), the content ratio of propane in the blowing agent is preferably from 0.1% by mass to 50% by mass, more preferably from 0.2% by mass to 45% by mass, still more preferably from 0.3% by mass to 40% by mass, particularly preferably from 0.4% by mass to 38% by mass, and most preferably from 0.4% by mass to 35% by mass.

[0078] In Embodiment (1), if the content of propane in the entire blowing agent to be press-fitted is too small or too large, the effect of the present invention may not be exhibited. For example, there may be variations in quality, leading to a decrease in moldability.

[0079] In Embodiment (1), the foaming agent to be press-fitted may contain, together with propane, an organic compound or an inorganic gas other than propane that has a boiling point equal to or lower than the softening point of the styrene resin and is gaseous or liquid at normal pressure, in terms of more effectively expressing the effects of the present invention. Examples of the organic compound include aliphatic hydrocarbons such as butane (n-butane, isobutane), pentane (n-pentane, isopentane, neopentane), and n-hexane; alicyclic hydrocarbons such as cyclopentane and cyclopentadiene; ketones such as acetone and methyl ethyl ketone; alcohols such as methanol, ethanol, and isopropyl alcohol; low-boiling ether compounds such as dimethyl ether, diethyl ether, dipropyl ether, and methyl ethyl ether; and halogen-containing hydrocarbons such as trichloromonofluoromethane and dichlorodifluoromethane. Examples of the inorganic gas include carbon dioxide gas, nitrogen, and ammonia. Among the above-mentioned organic compounds and inorganic gases, in terms of more effectively expressing the effects of the present invention, an organic compound that has a boiling point equal to or lower than the softening point of the styrene resin and is gaseous or liquid at normal pressure is preferable, and at least one selected from the group consisting of butane and pentane is more preferable, and pentane is particularly preferable. Therefore, in Embodiment (1), the foaming agent to be press-fitted preferably contains propane and at least one selected from the group consisting of butane and pentane, and more preferably contains propane and pentane, in terms of further expressing the effects of the present invention. Further, in Embodiment (1), the content ratio of the total amount of propane and at least one selected from the group consisting of butane and pentane in the foaming agent to be press-fitted is preferably 50% by mass to 100% by mass, more preferably 70% by mass to 100% by mass, still more preferably 90% by mass to 100% by mass, particularly preferably 95% by mass to 100% by mass, and most preferably substantially 100% by mass.

[0080] In Embodiment (1), when the foaming agent to be press-fitted contains at least one selected from the group consisting of butane and pentane, the press-fitting amount of at least one selected from the group consisting of butane and pentane is preferably 0.01% by mass or more, more preferably 0.1% by mass to 30% by mass, still more preferably 0.5% by mass to 20% by mass, particularly preferably 1.0% by mass to 15% by mass, and most preferably 2% by mass to 13% by mass, based on the recycled styrene resin particles (A).

[0081] In Embodiment (1), the content ratio of at least one selected from the group consisting of butane and pentane in the foaming agent to be press-fitted (in the total foaming agent used) is preferably 99.9% by mass or less, more preferably 50% by mass to 99.9% by mass, still more preferably 55% by mass to 99.8% by mass, particularly preferably 60% by mass to 99.7% by mass, and most preferably 65% by mass to 99.6% by mass.

[0082] In Embodiment (1), the press-fitting amount of the total foaming agent used can be appropriately set according to the purpose as long as it is sufficient to form the recycled pre-expanded styrene resin particles and the recycled styrene resin foam molded article. The press-fitting amount of the foaming agent is preferably 0.1% by mass to 40% by mass, more preferably 0.5% by mass to 27% by mass, still more preferably 1% by mass to 20% by mass, particularly preferably 2% by mass to 17% by mass, based on the recycled styrene resin particles (A).

[0083] In Embodiment (1), the pressure injection temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 50°C to 140°C, still more preferably 60°C to 130°C, still more preferably 70°C to 123°C, still more preferably 80°C to 115°C, particularly preferably 90°C to 110°C, and most preferably 95°C to 105°C. The pressure injection temperature of the foaming agent into the recycled styrene resin particles (A) may be varied within the above range. If the pressure injection temperature of the foaming agent into the recycled styrene resin particles (A) is within the above range, the rapid impregnation of the foaming agent into the recycled styrene resin particles (A) is suppressed, enabling uniform impregnation. For example, when molded into a recycled styrene resin foam molded article, the locations that shrink and melt can be reduced, and the odor peculiar to the recycled raw material can be more easily removed. If the pressure injection temperature of the foaming agent into the recycled styrene resin particles (A) is too low outside the above range, the foaming agent is difficult to impregnate into the recycled styrene resin particles (A) during the pressure injection of the foaming agent. For example, when the temperature is increased, the foaming agent is rapidly impregnated, the foaming agent is not uniformly impregnated into the recycled styrene resin particles (A), bubble variations are likely to occur, and surface shrinkage during molding may easily occur. If the pressure injection temperature of the foaming agent into the recycled styrene resin particles (A) is too high outside the above range, the foaming agent is rapidly impregnated into the recycled styrene resin particles (A) during the pressure injection of the foaming agent, the foaming agent is not uniformly impregnated into the recycled styrene resin particles (A), bubble variations are likely to occur, and surface shrinkage during molding may easily occur.

[0084] In Embodiment (1), one embodiment of the impregnation temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 40°C to 150°C, more preferably 40°C to 140°C, still more preferably 40°C to 130°C, still more preferably 40°C to 123°C, still more preferably 40°C or higher and less than 110°C, particularly preferably 40°C to 105°C, and most preferably 40°C to 102°C.

[0085] In Embodiment (1), another embodiment of the impregnation temperature of the blowing agent into the recycled styrene resin particles (A) is preferably a temperature equal to or higher than the pressure injection temperature of the blowing agent into the recycled styrene resin particles (A) (it may be the same as the pressure injection temperature of the blowing agent into the recycled styrene resin particles (A)), preferably 93°C to 130°C, more preferably 94°C to 129°C, still more preferably 95°C to 128°C, particularly preferably 96°C to 127°C, and most preferably 97°C to 126°C.

[0086] The impregnation temperature of the blowing agent into the recycled styrene resin particles (A) may be changed within the above range. If the impregnation temperature of the blowing agent into the recycled styrene resin particles (A) is within the above range, in combination with the adjustment of the above pressure injection temperature, the rapid impregnation of the blowing agent into the recycled styrene resin particles (A) can be suppressed, and uniform impregnation becomes possible. For example, when molded into a recycled styrene resin foam molded body, the locations where shrinkage and melting occur can be reduced. If the impregnation temperature of the blowing agent into the recycled styrene resin particles (A) is too low outside the above range, the blowing agent may not be impregnated to the center of the recycled styrene resin particles (A), leaving non-foamed portions, and there is a risk that a good molded product cannot be obtained. If the impregnation temperature of the blowing agent into the recycled styrene resin particles (A) is too high outside the above range, the blowing agent may be impregnated too much into the recycled styrene resin particles (A), and there is a risk of melting during molding.

[0087] In Embodiment (1), as a particularly representative embodiment of the impregnation temperature of the blowing agent into the recycled styrene resin particles (A), it is preferably 40°C to 150°C, more preferably 50°C to 130°C, still more preferably 60°C to 120°C, still more preferably 70°C or higher and less than 110°C, still more preferably 80°C or higher and less than 110°C, particularly preferably 90°C or higher and less than 110°C, and most preferably 95°C to 105°C.

[0088] The impregnation time of the blowing agent into the recycled styrene resin particles (A) can be any appropriate time as long as the effects of the present invention are not impaired. Such an impregnation time is preferably 1 hour to 10 hours.

[0089] <A-1-3. Other Components in Embodiment (1)> The recycled expandable styrenic resin particles in Embodiment (1) may contain any suitable other components as long as the effects of the present invention are not impaired. Such other components may be only one type or two or more types.

[0090] In producing the recycled expandable styrenic resin particles in Embodiment (1), a foaming aid may be used. That is, the recycled expandable styrenic resin particles in Embodiment (1) may contain a foaming aid. The foaming aid may be only one type or two or more types. Examples of the foaming aid include diisobutyl adipate, toluene, cyclohexane, ethylbenzene, liquid paraffin, and coconut oil.

[0091] The recycled expandable styrenic resin particles in Embodiment (1) may contain a flame retardant in order to enhance flame retardancy. The flame retardant may be only one type or two or more types.

[0092] As the flame retardant, any suitable flame retardant can be adopted as long as the effects of the present invention are not impaired. Such flame retardants preferably include bromine compounds compatible with polystyrene. For example, tetrabromoethane, tetrabromocyclooctane, hexabromocyclododecane, hexabromocyclohexane, tris(dibromopropyl) phosphate, tetrabromobisphenol A, tetrabromobisphenol F, tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether), tetrabromobisphenol A-bis(2,3-dibromopropyl ether), tetrabromobisphenol A-diglycidyl ether, 2,2-bis[4’(2’’,3’’-dibromoalkoxy)-3’,5’-dibromophenyl]-propane, tris(tribromophenoxy)triazine, 2,2-bis(4-allyloxy-3,5-dibromo)propane, and hexabromobenzene can be mentioned.

[0093] When using a flame retardant, a flame retardant aid may be used in combination. Examples of the flame retardant aid include cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, 2,3-dimethyl-2,3-diphenylbutane, and 3,4-dimethyl-3,4-diphenylhexane.

[0094] As the total usage amount of the flame retardant and the flame retardant aid, any appropriate usage amount can be adopted as long as the effects of the present invention are not impaired. Such a usage amount is preferably 0.1% by mass to 15% by mass, more preferably 0.2% by mass to 10% by mass, still more preferably 0.2% by mass to 5% by mass, and particularly preferably 0.2% by mass to 3% by mass with respect to the recycled styrene resin raw material particles (a).

[0095] The addition of the flame retardant can be carried out at any appropriate timing as long as the effects of the present invention are not impaired. In terms of more effectively expressing the effects of the present invention, the flame retardant is preferably added before injecting the foaming agent. By adding the flame retardant before injecting the foaming agent, the flame retardant can be added at a temperature as low as the temperature at which the foaming agent is injected, so that good spheroidization and excellent moldability of the obtained recycled foamed styrene resin particles can be achieved.

[0096] In terms of more effectively expressing the effects of the present invention, the addition temperature when adding the flame retardant is preferably 5°C to 120°C, more preferably 5°C to 118°C, still more preferably 5°C to 115°C, still more preferably 5°C to 113°C, still more preferably 5°C to 110°C, still more preferably 40°C to 89°C, still more preferably 40°C to 87°C, still more preferably 40°C to 85°C, particularly preferably 40°C to 83°C, and most preferably 40°C to 80°C.

[0097] In producing the recycled expandable styrenic resin particles in Embodiment (1), a partial ester of a higher fatty acid and an alcohol may be used. That is, the recycled expandable styrenic resin particles in Embodiment (1) may contain a partial ester of a higher fatty acid and an alcohol. The partial ester of a higher fatty acid and an alcohol may be only one kind or two or more kinds. Examples of the higher fatty acid include fatty acids having 15 or more carbon atoms such as palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and behenic acid, and monoglycerides and diglycerides thereof can be used. Preferred examples of the partial ester of a higher fatty acid and an alcohol include stearic acid monoglyceride and stearic acid diglyceride. The content ratio of the partial ester of a higher fatty acid and an alcohol is preferably from 0 parts by mass to 3.0 parts by mass with respect to 100 parts by mass of the recycled styrenic resin particles (A). As a method of adding the partial ester of a higher fatty acid and an alcohol, for example, it can be added together with a foaming agent, or a commonly used method such as a dry blend method, a masterbatch method, or a melt injection method can be adopted.

[0098] In producing the recycled expandable styrenic resin particles in Embodiment (1), a cell regulator may be used. That is, the recycled expandable styrenic resin particles in Embodiment (1) may contain a cell regulator. The cell regulator may be only one kind or two or more kinds. Examples of the cell regulator include fatty acid monoamides such as oleic acid amide, stearic acid amide, and hydroxystearic acid amide; fatty acid bisamides such as methylene bisstearic acid amide and ethylene bisstearic acid amide; citric acid; finely powdered inorganic substances such as talc, calcium carbonate, silica, mica, and sodium bicarbonate. Here, talc typically refers to a mixture mainly composed of silicon oxide and magnesium oxide and containing trace amounts of aluminum oxide, iron oxide, etc.

[0099] As the amount of the bubble regulator used, any appropriate amount can be adopted as long as the effects of the present invention are not impaired. Such an amount is preferably 0 part by mass to 5.0 parts by mass, more preferably 0 part by mass to 3.0 parts by mass, still more preferably 0 part by mass to 2.0 parts by mass, particularly preferably 0 part by mass to 1.0 part by mass, and most preferably 0 part by mass to 0.1 part by mass, based on 100 parts by mass of the recycled styrene resin particles (A).

[0100] In producing the recycled foamed styrene resin particles in Embodiment (1), even without using a bubble regulator, by containing a predetermined amount of propane having a high vapor pressure as the foaming agent, recycled foamed styrene resin particles with stable quality and excellent moldability can be provided. In particular, when propane is used in combination with at least one selected from the group consisting of butane and pentane, due to the above effects of propane, recycled foamed styrene resin particles with more stable quality and more excellent moldability can be provided.

[0101] Examples of other additives include pigments, radiation heat transfer suppression components, crosslinking agents, plasticizers, stabilizers, fillers, lubricants, colorants, antistatic agents, spreading agents, weathering agents, antioxidants, antifogging agents, and fragrances, in addition to these.

[0102] <A-1-4. Surface Treatment> The recycled foamed styrene resin particles in Embodiment (1) may be subjected to surface treatment. Such surface treatment is preferably surface treatment with at least one selected from silicone oil, antistatic agent, fatty acid metal salt, and fusion promoter.

[0103] When the recycled expandable styrene resin particles in Embodiment (1) are surface-treated with silicone oil, the amount of silicone oil used per 100 parts by mass of the recycled expandable styrene resin particles before the surface treatment is preferably 0.001 to 0.3 parts by mass, more preferably 0.003 to 0.28 parts by mass, still more preferably 0.005 to 0.25 parts by mass, particularly preferably 0.008 to 0.23 parts by mass, and most preferably 0.01 to 0.23 parts by mass. If the amount of silicone oil used is too small outside the above range, for example, when using an antistatic agent, the affinity with the antistatic agent may not be sufficient during pre-foaming, and there is a risk of easy generation of static electricity. If the amount of silicone oil used is too large outside the above range, there is a risk of losing surface properties due to melting of the surface during molding.

[0104] The silicone oil may be only one type or two or more types.

[0105] As the silicone oil, any appropriate silicone oil can be adopted as long as the effects of the present invention are not impaired. In terms of more expressing the effects of the present invention, examples of the silicone oil include straight silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, and methylhydrogenpolysiloxane, and preferably methylphenylpolysiloxane.

[0106] When the surface treatment with an antistatic agent is performed on the recycled expandable polystyrene resin particles in Embodiment (1), the amount of the antistatic agent used per 100 parts by mass of the recycled expandable polystyrene resin particles before the surface treatment is preferably 0.001 part by mass to 0.3 part by mass, more preferably 0.005 part by mass to 0.28 part by mass, still more preferably 0.01 part by mass to 0.27 part by mass, particularly preferably 0.015 part by mass to 0.26 part by mass, and most preferably 0.02 part by mass to 0.25 part by mass. If the amount of the antistatic agent is too small outside the above range, static electricity may easily be generated during pre-expansion. If the amount of the antistatic agent is too large outside the above range, the surfaces of the recycled pre-expanded polystyrene resin particles and the recycled polystyrene resin foam molded article may become sticky.

[0107] The antistatic agent may be only one kind or two or more kinds.

[0108] As the antistatic agent, any suitable antistatic agent can be adopted as long as the effects of the present invention are not impaired. In terms of being able to more manifest the effects of the present invention, the antistatic agent includes at least one selected from nonionic surfactants and fatty acid glycerides, and preferably, it is a combined use of a nonionic surfactant and a fatty acid glyceride.

[0109] The nonionic surfactant may be only one kind or two or more kinds.

[0110] As the nonionic surfactant, any appropriate nonionic surfactant can be employed as long as it does not impair the effects of the present invention. In terms of more effectively expressing the effects of the present invention, examples of the nonionic surfactant include polyethylene glycol, glycerin, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester, polyhydric alcohol, and 1-amino-2-hydroxy compound. Specific examples of the polyoxyethylene alkyl ether include polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, and polyoxyethylene stearyl ether. Specific examples of the polyoxyethylene alkyl ester include polyoxyethylene laurate, polyoxyethylene palmitate, polyoxyethylene stearate, and polyoxyethylene oleate. Specific examples of the polyhydric alcohol include glycerin and propylene glycol. Specific examples of the 1-amino-2-hydroxy compound include N-hydroxyethyl-N-(2-hydroxyalkyl)amine, N,N-bis(hydroxyethyl)dodecylamine, N,N-bis(hydroxyethyl)tetradecylamine, N,N-bis(hydroxyethyl)hexadecylamine, N,N-bis(hydroxyethyl)octadecylamine, N-hydroxyethyl-N-(2-hydroxytetradecyl)amine, N-hydroxyethyl-N-(2-hydroxyhexadecyl)amine, N-hydroxyethyl-N-(2-hydroxyoctadecyl)amine, N-hydroxypropyl-N-(2-hydroxytetradecyl)amine, N-hydroxybutyl-N-(2-hydroxytetradecyl)amine, N-hydroxypentyl-N-(2-hydroxytetradecyl)amine, N-hydroxypentyl-N-(2-hydroxyhexadecyl)amine, N-hydroxypentyl-N-(2-hydroxyoctadecyl)amine, N,N-bis(2-hydroxyethyl)dodecylamine, N,N-bis(2-hydroxyethyl)tetradecylamine, N,N-bis(2-hydroxyethyl)hexadecylamine, N,N-bis(2-hydroxyethyl)octadecylamine, and salts thereof.In terms of being able to more effectively exhibit the effects of the present invention, polyethylene glycol is preferable as the nonionic surfactant.

[0111] When a nonionic surfactant is employed as at least a part of the antistatic agent, the amount of the nonionic surfactant used with respect to 100 parts by mass of the recycled expandable styrene resin particles before surface treatment is preferably from 0.001 part by mass to 2.0 parts by mass, more preferably from 0.001 part by mass to 1.5 parts by mass, still more preferably from 0.001 part by mass to 1.0 parts by mass, still more preferably from 0.001 part by mass to 0.5 parts by mass, still more preferably from 0.001 part by mass to 0.3 parts by mass, still more preferably from 0.005 part by mass to 0.28 parts by mass, still more preferably from 0.01 part by mass to 0.27 parts by mass, particularly preferably from 0.015 part by mass to 0.26 parts by mass, and most preferably from 0.02 part by mass to 0.25 parts by mass. If the amount of the nonionic surfactant is too small outside the above range, static electricity is likely to be generated during pre-expansion. If the amount of the nonionic surfactant is too large outside the above range, the surfaces of the recycled pre-expanded styrene resin particles and the recycled styrene resin foam molded article may become sticky.

[0112] The fatty acid glyceride may be only one kind or two or more kinds.

[0113] As the fatty acid glyceride, any suitable fatty acid glyceride can be adopted as long as the effects of the present invention are not impaired. In terms of being able to more effectively exhibit the effects of the present invention, specific examples of the fatty acid glyceride include, for example, monoglyceryl stearate and monoglyceryl linoleate. In terms of being able to more effectively exhibit the effects of the present invention, monoglyceryl stearate is preferable as the fatty acid glyceride.

[0114] When a fatty acid glyceride is employed as at least a part of the antistatic agent, the amount of the fatty acid glyceride relative to 100 parts by mass of the recycled expandable styrene resin particles before the surface treatment is preferably from 0.001 part by mass to 0.3 part by mass, more preferably from 0.005 part by mass to 0.28 part by mass, still more preferably from 0.01 part by mass to 0.27 part by mass, particularly preferably from 0.015 part by mass to 0.26 part by mass, and most preferably from 0.02 part by mass to 0.25 part by mass. If the amount of the fatty acid glyceride is too small outside the above range, static electricity is likely to be generated during pre-expansion. If the amount of the fatty acid glyceride is too large outside the above range, the surfaces of the recycled pre-expanded styrene resin particles and the recycled styrene resin foam molded article may become sticky.

[0115] When the surface treatment of the recycled expandable styrene resin particles in Embodiment (1) is carried out with a fatty acid metal salt, the amount of the fatty acid metal salt used relative to 100 parts by mass of the recycled expandable styrene resin particles before the surface treatment is preferably from 0.005 part by mass to 0.5 part by mass, more preferably from 0.007 part by mass to 0.45 part by mass, still more preferably from 0.01 part by mass to 0.4 part by mass, particularly preferably from 0.015 part by mass to 0.35 part by mass, and most preferably from 0.02 part by mass to 0.3 part by mass. If the amount of the fatty acid metal salt is too small outside the above range, a lot of blocking may occur during pre-expansion, and it may not be possible to obtain a good styrene resin foam molded article. If the amount of the fatty acid metal salt is too large outside the above range, a large amount of the metal salt will be present during pre-expansion, making it easier to charge and generating static electricity, and the fusion of the molded article may deteriorate.

[0116] The fatty acid metal salt may be only one kind or two or more kinds.

[0117] As the fatty acid metal salt, any appropriate fatty acid metal salt can be employed as long as the effects of the present invention are not impaired. In terms of being able to more effectively exhibit the effects of the present invention, examples of the fatty acid metal salt include metal stearates and metal laurates. Specific examples of the metal stearate include magnesium stearate, calcium stearate, zinc stearate, barium stearate, aluminum stearate, and lithium stearate. Specific examples of the metal laurate include zinc laurate and barium laurate. In terms of being able to more effectively exhibit the effects of the present invention, magnesium stearate and zinc stearate are preferred as the fatty acid metal salt.

[0118] When the surface treatment with the fusion promoter is performed on the recycled foaming styrene resin particles in Embodiment (1), the amount of the fusion promoter used with respect to 100 parts by mass of the recycled foaming styrene resin particles before the surface treatment is preferably from 0.01 part by mass to 0.8 part by mass, more preferably from 0.01 part by mass to 0.7 part by mass, still more preferably from 0.01 part by mass to 0.6 part by mass, particularly preferably from 0.01 part by mass to 0.55 part by mass, and most preferably from 0.013 part by mass to 0.5 part by mass. If the amount of the fusion promoter is too small outside the above range, the fusibility during molding may decrease, and there is a risk that a good recycled styrene resin foamed molded article cannot be obtained. If the amount of the fusion promoter is too large outside the above range, there is a risk of blocking during pre-foaming.

[0119] The fusion promoter may be only one kind or two or more kinds.

[0120] As the fusion promoter, any appropriate fusion promoter can be employed as long as the effects of the present invention are not impaired. In terms of more effectively expressing the effects of the present invention, examples of the fusion promoter include fatty acid triglycerides, fatty acid diglycerides, fatty acid monoglycerides, and vegetable oils. Specific examples of the fatty acid triglycerides include, for example, lauric acid triglyceride, stearic acid triglyceride, linoleic acid triglyceride, and hydroxystearic acid triglyceride. Specific examples of the fatty acid diglycerides include, for example, lauric acid diglyceride, stearic acid diglyceride, and linoleic acid diglyceride. Specific examples of the fatty acid monoglycerides include, for example, lauric acid monoglyceride. Specific examples of the vegetable oils include, for example, hydrogenated castor oil. In terms of more effectively expressing the effects of the present invention, stearic acid triglyceride and hydroxystearic acid triglyceride are preferred as the fusion promoter.

[0121] ≪A-2. Preferred Embodiment (2) of Recyclable Expanded Styrene-Based Resin Particles≫ One preferred embodiment (2) of the recyclable expanded styrene-based resin particles of the present invention is recyclable expanded styrene-based resin particles obtained by press-fitting a foaming agent into recycled styrene-based resin particles (A), wherein the recycled styrene-based resin particles (A) are recycled styrene-based resin raw material particles (a).

[0122] <A-2-1. Recycled Styrene-Based Resin Particles (A) in Embodiment (2)> The recycled styrene-based resin particles (A) in Embodiment (2) are recycled styrene-based resin raw material particles (a). That is, in Embodiment (2), recycled styrene-based resin raw material particles (a) are used as the recycled styrene-based resin particles (A). Regarding the recycled styrene-based resin raw material particles (a) that can be employed as the recycled styrene-based resin particles (A) in Embodiment (2), the description of the recycled styrene-based resin raw material particles (a) in the section of <A-1-1. Recycled Styrene-Based Resin Particles (A) in Embodiment (1)> described above can be incorporated by reference.

[0123] <A-2-2. Pressurization of blowing agent in Embodiment (2)> The recycled expandable styrene resin particles in Embodiment (2) are obtained by pressurizing a blowing agent into recycled styrene resin particles (A) that directly use recycled styrene resin raw material particles (a). Typically, the blowing agent is pressurized and impregnated into the resin particles.

[0124] Typical methods for pressurizing the blowing agent in Embodiment (2) include Pressurization method (1): A suspension containing recycled styrene resin particles (A) (directly using recycled styrene resin raw material particles (a)) is placed in a reactor such as an autoclave, and the blowing agent is pressurized. Pressurization method (2): Recycled styrene resin particles (A) (directly using recycled styrene resin raw material particles (a)) are placed in an extruder, the blowing agent is pressurized midway in the extruder, and at the same time as being extruded from the extruder, it is cut in water. can be mentioned.

[0125] Regarding Pressurization method (1), the explanations in the section of <A-1-2. Pressurization of blowing agent in Embodiment (1)> described above can be cited. However, the pressurization temperature and impregnation temperature of the blowing agent into the recycled styrene resin particles (A) are as follows.

[0126] Regarding the press-fitting method (1) in Embodiment (2), the press-fitting temperature of the foaming agent into the recycled styrene-based resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 145°C, still more preferably 80°C to 140°C, particularly preferably 100°C to 135°C, and most preferably 110°C to 130°C. The press-fitting temperature of the foaming agent into the recycled styrene-based resin particles (A) may be varied within the above range. If the press-fitting temperature of the foaming agent into the recycled styrene-based resin particles (A) is within the above range, for example, even when the recycled styrene-based resin particles (A) are irregularly shaped particles, they are more likely to be spheroidized, the adhesion between particles can be reduced, and the odor peculiar to the recycled raw material can be easily removed. If the press-fitting temperature of the foaming agent into the recycled styrene-based resin particles (A) is too low outside the above range, it may be difficult to spheroidize them. If the press-fitting temperature of the foaming agent into the recycled styrene-based resin particles (A) is too high outside the above range, there is a risk of particle flattening or an increase in adhered particles.

[0127] Regarding the press-fitting method (1) in Embodiment (2), the impregnation temperature of the foaming agent into the recycled styrene-based resin particles (A) is preferably 40°C to 150°C, more preferably 60°C to 130°C, still more preferably 80°C to 120°C, still more preferably 90°C or higher and less than 110°C, particularly preferably 95°C or higher and less than 110°C, and most preferably 100°C or higher and less than 110°C. The impregnation temperature of the foaming agent into the recycled styrene-based resin particles (A) may be varied within the above range. If the impregnation temperature of the foaming agent into the recycled styrene-based resin particles (A) is within the above range, for example, the foaming agent is more likely to be efficiently impregnated into the recycled styrene-based resin particles (A), and the foaming agent is uniformly absorbed, so it becomes easier to control subsequent foaming and molding, and the odor peculiar to the recycled raw material can be easily removed. If the impregnation temperature of the foaming agent into the recycled styrene-based resin particles (A) is too low outside the above range, there is a risk that the foaming agent may not be absorbed to the center of the recycled styrene-based resin particles (A), or only a part of the press-fitted foaming agent can be absorbed by the recycled styrene-based resin particles (A). If the impregnation temperature of the foaming agent into the recycled styrene-based resin particles (A) is too high outside the above range, there is a risk of particle flattening or an increase in adhered particles.

[0128] The injection method (2) in Embodiment (2) is a method of putting recycled styrene resin particles (A) (using recycled styrene resin raw material particles (a) as they are) into an extruder, injecting a foaming agent halfway in the extruder, and simultaneously cutting in water when extruding from the extruder (water cutting method).

[0129] More specifically, the injection method (2) in Embodiment (2) supplies recycled styrene resin particles (A) (using recycled styrene resin raw material particles (a) as they are) to an extruder, heats and melts them, injects a foaming agent from the middle of the extruder, extrudes the resulting resin composition from a porous die into water, and cuts it in water simultaneously with the extrusion to obtain resin particles.

[0130] As the foaming agent, the description of the foaming agent in the item of <A-1-2. Injection of the foaming agent in Embodiment (1)> described above can be incorporated by reference.

[0131] Regarding the injection method (2) in Embodiment (2), the injection temperature of the foaming agent into the recycled styrene resin particles (A) is preferably 100°C to 300°C, more preferably 120°C to 290°C, still more preferably 150°C to 280°C, particularly preferably 160°C to 280°C, and most preferably 170°C to 260°C. The injection temperature of the foaming agent into the recycled styrene resin particles (A) may be changed within the above range. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is within the above range, for example, the foaming agent is likely to be efficiently injected into the recycled styrene resin particles (A), and the foaming agent is uniformly absorbed, so it becomes easier to control subsequent foaming and molding. If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is too low outside the above range, there is a risk that the foaming agent is not uniformly absorbed by the recycled styrene resin particles (A). If the injection temperature of the foaming agent into the recycled styrene resin particles (A) is too high outside the above range, there is a risk of an increase in particle agglomeration and flattening.

[0132] When cutting underwater simultaneously with extrusion, the water temperature is preferably 15°C to 60°C, more preferably 20°C to 50°C. When the water temperature is lower than 15°C, the cooling on the die surface becomes stronger, the die holes are likely to be blocked, and the pressure inside the die may increase, making extrusion difficult. When the water temperature is higher than 60°C, it may be difficult to suppress foaming. Furthermore, when the water temperature exceeds 80°C, the resin particles obtained by cutting may easily adhere together.

[0133] The water temperature is preferably 100°C to 200°C lower than the temperature of the resin composition at the time of die inflow. When the temperature difference between the water temperature and the resin composition temperature is less than 100°C, the cooling of the resulting resin particles may be insufficient, and it may be difficult to suppress foaming. When the temperature difference between the water temperature and the resin composition temperature exceeds 200°C, the resin particles may be deformed due to the temperature difference between the surface and the inside of the resulting resin particles, and may not become spherical.

[0134] In the underwater cutting method, 50 to 500 die ejection holes are used, and preferably, the water pressure is adjusted to 0 MPa to 2.00 MPa and the ejection rate is adjusted to 50 kg / hour to 300 kg / hour. In the underwater cutting method, the water pressure corresponds to the resistance when the resin is extruded from the die into the water, and the ejection rate corresponds to the force in the extrusion direction when the resin composition is extruded from the die into the water. Therefore, in the underwater cutting method, by appropriately adjusting the water pressure and the ejection rate, expandable polystyrene resin particles can be produced well. In particular, when using a recycled polystyrene resin as the resin component, due to the thermal history received during recycling, the molecular weight tends to decrease and the fluidity tends to increase accordingly. Also, since the additives derived from the recycled raw materials contain arbitrary amounts, the fluidity and viscoelasticity change, and precise adjustment of the water pressure and the ejection rate in the underwater cutting method is required.

[0135] The water pressure in the underwater cutting method is preferably from 0.12 MPa to 1.90 MPa, more preferably from 0.13 MPa to 1.85 MPa, still more preferably from 0.15 MPa to 1.80 MPa, and particularly preferably from 0.20 MPa to 1.60 MPa.

[0136] The discharge amount in the underwater cutting method is preferably from 60 kg / hour to 280 kg / hour, more preferably from 80 kg / hour to 270 kg / hour, still more preferably from 100 kg / hour to 260 kg / hour, and particularly preferably from 120 kg / hour to 250 kg / hour.

[0137] An example of an apparatus suitable for producing the regenerated foamed polystyrene resin particles in Embodiment (2) by the underwater cutting method of the pressing method (2) is shown in Fig. 1. This production apparatus includes a raw material supply hopper 11 for introducing a resin component (B) upstream in the resin flow direction (the direction from left to right in Fig. 1), a foaming agent supply port 12 having a high-pressure pump 13 downstream of the resin flow direction from the raw material supply hopper 11, an extruder 1 provided with a porous die 2 at the end of the resin flow direction, a cutting chamber 3 provided so as to cover the outlet of the porous die 2, in which a cutter 31 is rotatably arranged and which is configured to circulate water inside, a water tank 6 and a water supply pump 4 for supplying water to the cutting chamber 3, a dehydration dryer 5 for introducing the regenerated foamed polystyrene resin particles cut in the cutting chamber 3 together with water and separating the water and the regenerated foamed polystyrene resin particles, and a container 7 for storing the regenerated foamed polystyrene resin particles separated by the dehydration dryer 5.

[0138] As the extruder 1, a known extruder used in the extrusion molding of a resin composition can be used. Examples of such an extruder include a single-screw extruder, a twin-screw extruder, and a tandem extruder. The extruder 1 feeds the resin component (B) from the raw material supply hopper 11, heats and kneads it in the extruder 1, and transfers the melt-kneaded material downstream in the resin flow direction. When the melt-kneaded material reaches the foaming agent supply port 12, the foaming agent pumped by the high-pressure pump 13 is mixed with the melt-kneaded material. Thereafter, the obtained resin composition is extruded from the porous die 2 into the cutting chamber 3, comes into contact with water, and is cut by the cutter 31 in the water. The cut resin composition becomes spherical particles with substantially uniform particle diameters and is conveyed from the cutting chamber 3 to the dehydration dryer 5 by the circulating water flow. The recycled expandable polystyrene resin particles obtained by separating and drying from water in the dehydration dryer 5 are stored in the container 7, while the water is sent to the water tank 6.

[0139] <A-2-3. Other Components in Embodiment (2)> The recycled expandable polystyrene resin particles in Embodiment (2) may contain any appropriate other components as long as the effects of the present invention are not impaired. Such other components may be only one kind or two or more kinds.

[0140] As the other components, the descriptions in the item of <A-1-3. Other Components in Embodiment (1)> described above can be cited.

[0141] <A-2-4. Surface Treatment> The recycled expandable polystyrene resin particles in Embodiment (2) may be subjected to surface treatment. As such surface treatment, the descriptions in the item of <A-1-4. Surface Treatment> described above can be cited.

[0142] ≪≪B. Recycled Pre-expanded Polystyrene Resin Particles≫≫ The recycled pre-expanded polystyrene resin particles according to the embodiment of the present invention are obtained by pre-expanding the recycled expandable polystyrene resin particles according to the embodiment of the present invention.

[0143] The regenerated pre-expanded polystyrene resin particles preferably have an average cell diameter of 0.01 mm to 1.10 mm, more preferably 0.01 mm to 1.00 mm, still more preferably 0.01 to 0.90 mm, particularly preferably 0.01 mm to 0.80 mm, and most preferably 0.01 mm to 0.70 mm. If the average cell diameter of the regenerated pre-expanded polystyrene resin particles is within the above range, blocking during foaming and molding can be more effectively prevented. Furthermore, while suppressing the chargeability during foaming and molding, better fusion properties and surface properties can be exhibited, and a regenerated polystyrene resin foam molded article with less static electricity can be molded, thus providing regenerated pre-expanded polystyrene resin particles. If the average cell diameter of the regenerated pre-expanded polystyrene resin particles is less than 0.01 mm, the surface may melt and shrink during molding.

[0144] Pre-expansion includes foaming the regenerated foamable polystyrene resin particles to a desired bulk expansion ratio (bulk density) using steam or the like. The bulk expansion ratio of the regenerated pre-expanded polystyrene resin particles is preferably 2 to 150 times, more preferably 2 times or more and less than 100 times, still more preferably 5 to 90 times, further preferably 10 to 85 times, and particularly preferably 15 to 83 times. The bulk density is the reciprocal of the bulk expansion ratio. By having the bulk expansion ratio of the regenerated pre-expanded polystyrene resin particles within the above range, blocking during foaming and molding can be more effectively prevented. Furthermore, while suppressing the chargeability during foaming and molding, better fusion properties and surface properties can be exhibited, and a regenerated polystyrene resin foam molded article with less static electricity can be molded, thus providing regenerated pre-expanded polystyrene resin particles.

[0145] In one representative embodiment, the recycled pre-expanded polystyrene resin particles can be used for molding a recycled polystyrene resin foam molded article. In another embodiment, the recycled pre-expanded polystyrene resin particles can be used as they are as a cushioning material, a heat insulating material, an aggregate for concrete, or the like. When the recycled pre-expanded polystyrene resin particles are used as they are, the recycled pre-expanded polystyrene resin particles can preferably be used as a filled body in which a large number of recycled pre-expanded polystyrene resin particles are filled in a bag. Such recycled pre-expanded polystyrene resin particles are suitable, for example, as a core material of a cushion (expanded particles filled inside the cushion).

[0146] ≪≪C. Recycled polystyrene resin foam molded article≫≫ The recycled polystyrene resin foam molded article according to one embodiment of the present invention is a recycled polystyrene resin foam molded article formed from the recycled foamable polystyrene resin particles according to the embodiment of the present invention. The recycled polystyrene resin foam molded article according to another embodiment of the present invention is a recycled polystyrene resin foam molded article formed from the recycled pre-expanded polystyrene resin particles according to the embodiment of the present invention.

[0147] The recycled polystyrene resin foam molded article typically includes recycled expanded polystyrene resin particles (hereinafter, may be simply referred to as "expanded particles") obtained by further expanding the recycled pre-expanded polystyrene resin particles.

[0148] The recycled polystyrene resin foam molded article is typically composed of a plurality of expanded particles fused to each other.

[0149] The recycled styrene resin foam molded body can typically be produced by charging recycled pre-expanded styrene resin particles into a mold having a predetermined shape according to the purpose and performing in-mold foam molding. More specifically, in-mold foam molding includes: (i) filling the recycled pre-expanded styrene resin particles into a closed mold having a large number of small holes; (ii) heating and foaming the recycled pre-expanded styrene resin particles with a heat medium (for example, pressurized steam, etc.) to obtain foamed particles; (iii) filling the voids between the foamed particles and integrating them by fusing the foamed particles to each other by the heating and foaming. The density of the recycled styrene resin foam molded body can be appropriately set according to the purpose. The density of the recycled styrene resin foam molded body can be adjusted, for example, by preliminarily adjusting the bulk expansion ratio of the pre-expanded styrene resin particles filled in the mold, or by adjusting the filling amount of the recycled pre-expanded styrene resin particles into the mold.

[0150] The temperature of the heating and foaming (substantially the temperature of the heat medium) is preferably 90°C to 150°C, more preferably 110°C to 130°C. The heating and foaming time is preferably 5 seconds to 50 seconds, more preferably 10 seconds to 50 seconds. The forming steam pressure (the blowing gauge pressure of the heat medium) of the heating and foaming is preferably 0.04 MPa to 0.1 MPa, more preferably 0.06 MPa to 0.08 MPa. If the heating and foaming are under such conditions, the foamed particles can be well fused to each other.

[0151] If necessary, the recycled pre-expanded styrene resin particles may be aged before forming the recycled styrene resin foam molded body. The aging temperature of the recycled pre-expanded styrene resin particles is preferably 20°C to 60°C. If the aging temperature is too low, an excessively long aging time may be required. If the aging temperature is too high, the blowing agent in the recycled pre-expanded styrene resin particles may dissipate and the moldability may decrease.

[0152] The expansion ratio of the foamed particles in the recycled styrene resin foam molded body is preferably 2 times or more and less than 110 times, more preferably 5 times to 90 times, still more preferably 10 times to 85 times, and particularly preferably 15 times to 80 times.

[0153] The foamed styrene resin molded article according to the embodiment of the present invention is lightweight, excellent in heat insulation and mechanical strength, and thus is suitable for use as a heat insulating material for walls, a heat insulating material for floors, a heat insulating material for roofs, a heat insulating material for automobiles, a heat insulating material for hot water tanks, a heat insulating material for pipes, a heat insulating material for solar systems, a heat insulating material for water heaters, containers for foods and industrial products (for example, food containers such as fish boxes, shipping boxes), cushioning materials, floats, blocks, packaging materials for fish and agricultural products, molded articles for embankments, core materials for tatami mats, core materials for cushions, aggregates for concrete, etc.

Examples

[0154] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods and evaluation methods for each property are as follows.

[0155] <Measurement of the content of the blowing agent> The content (mass%) of the blowing agent in the recycled foaming styrene resin particles was measured as follows using a gas chromatograph and a gas chromatogram. Approximately 6 mg of the recycled foaming styrene resin particles were precisely weighed as a sample and set at the decomposition furnace inlet of the "PYR-1A" thermal decomposition furnace manufactured by Shimadzu Corporation. The mixed gas at the time of sample setting was discharged by purging with nitrogen for about 15 seconds. After sealing, the sample was inserted into the furnace core at 180°C to 200°C and heated for 120 seconds to release the gas. This released gas was measured using a "GC-14B (detector: FID)" gas chromatograph manufactured by Shimadzu Corporation. The content of the blowing agent was quantified using the peak area of the obtained gas chromatogram. <Measurement conditions> Measuring device: "GC-14B" gas chromatograph manufactured by Shimadzu Corporation Column: "Shimalite60 / 80NAW (Squalane25%) 3m × 3φ (I.D.SUS))" manufactured by Shinwa Chemical Industries Co., Ltd. Detector: FID (hydrogen flame ionization detector) Measurement conditions: Column temperature (70 °C), injection port temperature (110 °C), detector temperature (110 °C), heating furnace temperature (180 °C to 200 °C) Carrier gas (N2), N2 flow rate (50 mL / min), absolute calibration curve method

[0156] <Formability evaluation> The formability was evaluated by visually observing the appearance of the obtained foamed molded article. Specifically, it was evaluated based on the appearance of the surface (300 mm × 400 mm surface) of a plate-shaped recycled styrene-based resin foamed molded article with dimensions of 300 mm in length × 400 mm in width × 30 mm in thickness. The evaluation criteria were as follows. 〇: The depression of the foamed particles occurs on a surface area of 10% or less of the surface. △: The depression of the foamed particles occurs on a surface area of more than 20% and less than 30% of the surface. ×: The depression of the foamed particles occurs on a surface area of 30% or more of the surface. The smaller the depression of the foamed particles, the better the formability of the foamed molded article, indicating that the quality of the recycled foaming styrene-based resin particles and the recycled pre-expanded styrene-based resin particles as raw materials is stable.

[0157] [Production Example 1]: Production of recycled styrene-based resin raw material particles (a) The recovered pellets of used fish boxes were supplied to a single-screw extruder, heated and melted at 200 °C, then extruded from a mold and cut in water so that the average particle diameter was 0.75 mm (substantially spherical), thereby producing recycled styrene-based resin raw material particles (a).

[0158] [Example 1] <Production of recycled foaming styrene-based resin particles (1)>[[]] Into a 100-liter stirred reactor, 36 kg of water, 3.5 g of sodium dodecylbenzenesulfonate, and 150 g of magnesium pyrophosphate were added. Further, 12.6 kg of the recycled styrene-based resin raw material particles (a) obtained in Production Example 1 were added, and the mixture was stirred at 150 rpm to be suspended to prepare a suspension (1). Separately, 2.3 kg of styrene monomer in which 125 g of benzoyl peroxide (purity 75%) and 20 g of t-butylperoxy-2-ethylhexyl monocarbonate as polymerization initiators were dissolved was added to a dispersion of 2.5 kg of water and 0.8 g of sodium dodecylbenzenesulfonate, and the mixture was stirred with a homomixer to be emulsified to prepare an emulsion (1). The above suspension (1) in a 100-liter reactor equipped with a stirrer was maintained at 75°C, and the above emulsion (1) was added. Then, it was maintained at 75°C for 30 minutes so that the styrene monomer and the polymerization initiator were well absorbed into the recycled styrene-based resin raw material particles (a). Immediately after the holding, 27.1 kg of styrene monomer was continuously added dropwise over 120 minutes. The addition temperature was gradually increased from 75°C to 105°C. Thereafter, the temperature was raised to 125°C over 30 minutes, maintained at 125°C for 30 minutes, and then cooled to 60°C over 1 hour. Thereby, recycled styrene-based resin particles (A1) were prepared in the reaction vessel. Next, separately, 189 g of dicumyl peroxide and 35 g of ethylene bisstearamide were added to a dispersion of 3.5 kg of water, 1.5 g of sodium dodecylbenzenesulfonate, and 20 g of magnesium pyrophosphate, and the mixture was stirred with a homomixer to be emulsified to prepare an emulsion (2). This emulsion (2) was added to the reactor cooled to 60°C above. Ten minutes after this addition, 756 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60°C for 30 minutes. Subsequently, the temperature was raised to 100°C, and 7.5% by mass of pentane (isopentane / n-normal pentane = 20% by mass / 80% by mass) and 0.01% by mass of propane as foaming agents were press-fitted into the recycled styrene-based resin particles (A1), and the foaming agents were slowly impregnated by holding in that state for 5.5 hours. Then, the temperature in the reactor was cooled to 30°C. Thereafter, the content was taken out from the reactor, dehydrated, dried, and classified to obtain resin particles (1). The obtained resin particles (1) were stored in a cold storage at 15°C to obtain recycled expandable styrene-based resin particles (1).

[0159] <Surface Treatment of Recycled Expansible Polystyrene Resin Particles (1)> For the obtained aged recycled expansible polystyrene resin particles (1), 0.02% by mass of polyethylene glycol, 0.1% by mass of zinc stearate, 0.03% by mass of fatty acid triglyceride, and 0.04% by mass of fatty acid monoglyceride were put into a tumbler mixer and stirred for 30 minutes for surface treatment to obtain surface-treated recycled expansible polystyrene resin particles (1’).

[0160] <Preparation of Recycled Pre-expanded Polystyrene Resin Particles (1)> The obtained surface-treated recycled expansible polystyrene resin particles (1’) were put into a cylindrical batch foaming machine with a volume of 25 liters and heated with steam to obtain recycled pre-expanded polystyrene resin particles (1). The bulk density of the recycled pre-expanded polystyrene resin particles (1) was 0.017 g / cm 3 , and the expansion ratio was 60 times.

[0161] <Preparation of Recycled Polystyrene Resin Foamed Molding (1)> A molding machine having a mold with a cavity of 300 mm in length × 400 mm in width × 30 mm in thickness was used. The recycled pre-expanded polystyrene resin particles (1) were left standing at room temperature for 24 hours and then filled into the cavity of the mold of the above molding machine and heated at a steam pressure of 0.07 MPa (gauge pressure) for 30 seconds. Then, after cooling until the pressure in the mold reached 0.01 MPa, it was demolded from the mold to obtain a plate-shaped recycled polystyrene resin foamed molding (1) corresponding to the mold. The density of the recycled polystyrene resin foamed molding (1) was 0.017 g / cm 3 , and the expansion ratio was 60 times. Then, this recycled polystyrene resin foamed molding (1) was stored in a drying chamber at 50 °C for 1 day. The results are shown in Table 1.

[0162] [Examples 2 to 9] Except for changing the foaming agent as shown in Table 1, the procedure was the same as in Example 1, and recycled polystyrene resin particles (A1), recycled expandable polystyrene resin particles (2) to (9), recycled pre-expanded polystyrene resin particles (2) to (9), and recycled polystyrene resin foamed molded articles (2) to (9) were obtained. The results are shown in Table 1.

[0163] [Comparative Example 1] Except for changing the foaming agent as shown in Table 1, the procedure was the same as in Example 1, and recycled polystyrene resin particles (A1), recycled expandable polystyrene resin particles (C1), recycled pre-expanded polystyrene resin particles (C1), and recycled polystyrene resin foamed molded article (C1) were obtained. The results are shown in Table 1.

[0164] [Example 10] [Preparation of Recycled Expandable Polystyrene Resin Particles (10)] Into a 100-liter reactor equipped with a stirrer, 42 kg of water, 5.7 g of sodium dodecylbenzenesulfonate, and 295 g of magnesium pyrophosphate were added. Further, 42 kg of the recycled polystyrene resin raw material particles (a) obtained in Production Example 1 as the recycled polystyrene resin particles (A10) were added and stirred at 150 rpm to suspend them, and a suspension (3) was prepared. The suspension (3) in the 100-liter reactor equipped with a stirrer was maintained at 60°C, and 189 g of dicumyl peroxide and 35 g of ethylene bisstearamide were added. Ten minutes after this addition, 756 g of tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) was added. After the addition, stirring was continued at 60°C for 30 minutes. Thereafter, the temperature was raised to 120°C over 60 minutes. Subsequently, with respect to the recycled polystyrene resin particles (A10), 7.5% by mass of pentane (isopentane / n-normal pentane = 20% by mass / 80% by mass) and 0.01% by mass of propane as foaming agents were press-fitted, and after making it 108°C over 10 minutes, it was held in that state for 5 hours to slowly impregnate the foaming agent. Thereafter, the temperature inside the reactor was cooled to 30°C. Thereafter, the contents were taken out from the reactor, dehydrated, dried, and classified to obtain resin particles (10). The obtained resin particles (10) were stored in a cold storage at 15°C to obtain regenerated expandable polystyrene resin particles (10).

[0165] <Surface treatment of the regenerated expandable polystyrene resin particles (10)> To the obtained aged regenerated expandable polystyrene resin particles (10), 0.02% by mass of polyethylene glycol, 0.1% by mass of zinc stearate, 0.03% by mass of fatty acid triglyceride, and 0.04% by mass of fatty acid monoglyceride were added to a tumbler mixer and stirred for 30 minutes for surface treatment to obtain surface-treated regenerated expandable polystyrene resin particles (10').

[0166] <Preparation of pre-expanded regenerated polystyrene resin particles (10)> The obtained surface-treated regenerated expandable polystyrene resin particles (10') were put into a cylindrical batch foaming machine with a volume of 25 liters and heated with steam to obtain pre-expanded regenerated polystyrene resin particles (10). The bulk density of the pre-expanded regenerated polystyrene resin particles (10) was 0.017 g / cm 3 , and the bulk expansion ratio was 60 times.

[0167] <Preparation of the regenerated polystyrene resin foam molded article (10)> A molding machine having a mold with a cavity of 300 mm in length × 400 mm in width × 30 mm in thickness was used. The pre-expanded regenerated polystyrene resin particles (10) were left standing at room temperature for 24 hours and then filled into the cavity of the mold of the above molding machine, heated at a steam pressure of 0.07 MPa (gauge pressure) for 30 seconds, and then cooled until the pressure in the mold reached 0.01 MPa, and then released from the mold to obtain a plate-shaped regenerated polystyrene resin foam molded article (10) corresponding to the mold. The density of the regenerated polystyrene resin foam molded article (8) was 0.017 g / cm 3 , and the expansion ratio was 60 times. Then, this regenerated polystyrene resin foam molded article (10) was stored in a drying chamber at 50°C for 1 day. The results were shown in Table 2.

[0168] [Examples 11 to 18] Except for changing the blowing agent as shown in Table 2, the procedure was the same as in Example 10, and recycled polystyrene resin particles (A10), recycled expandable polystyrene resin particles (11) to (18), recycled pre-expanded polystyrene resin particles (11) to (18), and recycled polystyrene resin foamed molded articles (11) to (18) were obtained. The results are shown in Table 2.

[0169] [Comparative Example 2] Except for changing the blowing agent as shown in Table 2, the procedure was the same as in Example 8, and recycled polystyrene resin particles (A8), recycled expandable polystyrene resin particles (C2), recycled pre-expanded polystyrene resin particles (C2), and recycled polystyrene resin foamed molded article (C2) were obtained. The results are shown in Table 2.

[0170]

Table 1

[0171]

Table 2

Industrial Applicability

[0172] The recycled expandable polystyrene resin particles, recycled pre-expanded polystyrene resin particles, and recycled polystyrene resin foamed molded articles according to the embodiments of the present invention are suitably used as heat insulating materials for use in housing, automobiles, etc., heat insulating materials for use in building materials, etc., transport packaging materials such as fish boxes and food containers, cushioning materials, etc. More specifically, the recycled expandable polystyrene resin particles, recycled pre-expanded polystyrene resin particles, and recycled polystyrene resin foamed molded articles according to the embodiments of the present invention are wall heat insulating materials, floor heat insulating materials, roof heat insulating materials, automobile heat insulating materials, hot water tank heat insulating materials, pipe heat insulating materials, solar system heat insulating materials, water heater heat insulating materials, containers for foods and industrial products (e.g., food containers such as fish boxes, tote boxes), cushioning materials, floats, blocks, packaging materials for fish and agricultural products, embankment materials (such as embankment blocks), tatami core materials, cushion core materials, concrete aggregates, etc.

Explanation of Symbols

[0173] 1 Extruder 2 Multi-hole die 3 Cutting chamber 4 Water supply pump 5 Dehydration dryer 6 Water tank 7 Container 11 Raw material supply hopper 12 Blowing agent supply port 13 High-pressure pump 31 Cutter

Claims

1. Recycled expandable polystyrene resin particles with a propane content of 0.001% by mass or more.

2. The recycled expandable polystyrene resin particles according to Claim 1, obtained by press-fitting a blowing agent into recycled polystyrene resin particles (A).

3. The recycled expandable polystyrene resin particles according to Claim 2, wherein the press-fitted blowing agent contains propane and the press-fitting amount of the propane is 0.01% by mass or more based on the recycled polystyrene resin particles (A).

4. The recycled expandable polystyrene resin particles according to Claim 2, wherein the recycled polystyrene resin particles (A) are obtained by core-polymerizing a styrene monomer with recycled polystyrene resin raw material particles (a) as a core.

5. The recycled expandable polystyrene resin particles according to Claim 2, wherein the recycled polystyrene resin particles (A) are recycled polystyrene resin raw material particles (a).

6. Recycled pre-expanded polystyrene resin particles obtained by pre-expanding the recycled expandable polystyrene resin particles according to any one of Claims 1 to 5, wherein the bulk expansion ratio of the pre-expansion is 2 to 150 times. Recycled pre-expanded polystyrene resin particles.

7. A recycled polystyrene resin foam molded article formed from the recycled pre-expanded polystyrene resin particles according to Claim 6.

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